Naltrexone has been shown to have a therapeutic role in the rehabilitation of heroin addicts who are motivated to remain abstinent. The NAS-NRC cooperative study has demonstrated that Naltrexone is safe and that addicts maintained on Naltrexone use less illicit drugs, attend clinics more regularly, and have less craving for heroin. Unfortunately, efforts to keep addicts on Naltrexone for sustained periods have been unsuccessful. Although addicts previously exposed to Naltrexone treatment do show interest in returning to this treatment subsequently when the risk of physical readdiction becomes imminent. Intermittent use of Naltrexone under these circumstances has not yet been systematically studied. We believe that it may be quite useful and more practical in actual clinical practice and propose to examine this mode of Naltrexone use in the context of a comprehensive treatment program to see whether used in this way Naltrexone can be effective in those areas previously demonstrated and further, whether it can prevent the development of actual physical dependence and avert those adverse medical, legal and social consequences even though the addict may not be totally abstinent.